Why wouldn't two cations form a covalent bond?

How have the greenhouse gasses increased from the year 2000 to 2018

An engineer decides to use a slightly weaker material rather than a stronger material, since she knows that the stronger material can break suddenly. this is an example of what? a choosing a material that will show warning before it fails b using composite materials that combine strength c using a material for multiple applications d using design techniques that increase efficiency and reduce cost

Acompound has the molecular formula c3h8. which class of organic compounds does it belong to?